Device of the kind comprising an electronic tube having a ribbonshaped beam which is deflected and held in different positions



K. RODENHUIS June 16, 1953 2,6425547 DEVICE OF THE KIND COMPRISING AN ELECTRONIC TUBE, HAVING A RIBBON-SHAPED BEAM WHICH IS DEFLECTED AND HELD IN DIFFERENT POSITIONS Flled Nov 21, 1951 INVENTOR KLAAS" RODENHUIS- AGENT Patented June 16, 1953 j UNITED DEVICE OF THE KIND COMPRISING AN ELECTRONIC TUBE HAVING A RIBBON- SHAPED BEAM WHICH IS DEFLECTED AND HELD IN DIFFERENT POSITIONS Klaas Rodenhuis, Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application November 21, 1951, Serial No. 257,512 In the Netherlands November 30, 1950 The invention relates to devices of the kind comprising an electric discharge tube having a ribbon-shaped beam which can be deflected and held in different positions by current distribution.

With such a device, which may, for example, be used for counting pulses, it is of great impor tance to be able to read the position of the beam quickly and accurately. For this purpose provision is made of means to render the beam position optically visible, for example, a fluorescent screen, if necessary, in conjunction with means revealing the numerals corresponding to the different positions. It has been suggested to use, for this purpose, surface parts alternating in a given manner or luminescent numerals.

In such devices the beam passes, upon deflection, wholly or in part a plurality of electrodes, inter alia grids. In order to ensure an optimum operation of the device, these grids are arranged in a manner such that the wires or rods extend parallel to the direction of deflection of the beam.

In this case there is frequently a limitation in that shadows of the grid wires are visible on the fluorescent screen, which is a source of trouble when reading the position of the beam. A further difficulty is experienced in more or less vague instead of being sharp, whilst adjacent parts sometimes may also become luminescent. This also renders the reading of the beam position more difiicult. It has been found that this drawback is due to the fact that the edges of the beam portions passing through slots and apertures of different electrodes are frequently not sharply defined, inter alia because thatthe' edges of the luminescent surface parts may be 5 Claims. (Cl. 313-82) part, through a deflection system, a grid which is at low potential or at zero potential and of which the wires extend parallel to the direction of deflection of the beam, through a slotted screen, one or more grids and perforated electrodes, provision being made of means to render the position of the beam optically visible, the

partial beam currents formed by the first grid,

which is next to the deflection system and which is at low or zero potential, are focussedapproximately in the plane of the slotted screen, whilst viewed in the direction of travel of the electrons behind the slotted screen, there is a second grid at low or at zero potential, the wires of which are located in the shadow of those of the first grid, behind which are provided one or more partially perforated electrodes and means to render the position of the beam optically visible, the arrangement being such that the partial beam currents overlap one another in the area of the optical means, so that a sharply defined image of the beam position, which is luminescent throughout its surface, is produced.

The grid arranged behind the slotted screen must have such a Wire thickness and be at such a distance from the slotted screen that the electron paths behind this grid are spread in a manner such that the maximum uniformity of luminescence of the surface part associated with the given beam position is obtained. The apertures Of the anode are preferably covered by gauze of flne mesh. Thus the part of the beam current which flows to the optical means and which must be regarded as lost for the further operation of the device, is reduced and, moreover, since the apparent shadow ratio of gauze is greater for small angles of incidence, the strongly deflected stray electrons and peripheral electrons will be intercepted for the major part, whereas the electrons arriving at right angles at the gauze are allowed to pass for a greater part. Moreover, owing to the gauze, the potential in the apertures becomes substantially equal to that of the plate-shaped portion of the electrode, so that'there is no deflection of the passing electrons at the edge of the apertures. The size of the apertures of the anode and the gauze is chosen to be such that less than 20% of the beam current passes through the anode and finds its way to the optical means. If the reproduction is obtained by the luminescence of part of a fluorescent screen applied to the tube wall,

the screen must be prevented from taking anegative charge. A-bright luminescence requires that the electrons should iimpinge upon the This is avoided by providing a conductive, transparent, layer be tween the screen and the substratum, i. e. in this case the glass bulb of the tube and by connecting this layer to a point of high positive potential. The use of such layers incathode-ray tubes is known per so. In the present case a tin-oxide layer is found to be very suitable; it is conductively connected to a post-acceleration electrode, if any, or otherwise, to a further point of high positive potential.

Instead of comprising a fluorescent screen, the

means for rendering the beam position optically visible may, as an alternative, comprise windows in an anode coated with fluorescentmaterial, or the like.

In order to allow a rapid identificationzofithe' position of the beam, opaquemasks may be ap-. plied with advantage to the outer isidjeqor the. bulb, these masks having transparent numerals, which are arranged exactly in front of the associated luminescent surface parts. Very suitable are masks of celluloid,.-which is photographically blackened, the numeral being left transparent. This has the advantage that the numerals; can be accurately arranged on the luminescent sunface parts. Since, owing to inaccuracy of the tube construction, the position of the surfaceparts cannot always be exactly defined beforehand, the use of' separate masks is very advantageous, whilst by replacing the mask the indication of the beamposition may be shown by othersymbols.

In order that the invention may be readily carried into efiect,,an examplewill nowbe described in detail with reference. to the accompanying drawings, in which;

Fig. 1 is .a longitudinal sectionalview and Fig. 2 is a cross sectional view ofone embodimentiof the invention.

R ferrin o the fi ures. desi ates an electron sun, 2 a deflection pl te, 3 a id, d at zero potential or at a low positive or negative p nt a peratin as :a ollectinsr d to suppr ss secondary em sion fr m the slott d screen 4- to the deflection system-andi designates a grid which is constructed in. acmahnerzsimilarto the rid 3 and; which .iszarransedin a manner such that its. wires are located in the sha ow .ofho of the grid 3. Thegri si and. .4 rerprefera lv arranged in a manner such that the foci of, the partial beamv currents are located, approximately in the plane of the slotted screen 4, since in this case divergences in size, and positionpf the slot exert little influence on the passingfbeam current. The anode '6, Which-is connected to the output circuit, has a plurality of apertures, which are covered by gauze l in -a.man nersuch that about 8 to 10% of the current reaching this anode passes through the gauze and-reaches the fluorescent screen 9 by way the'post acceleration anode 8. Between this screen 9, and=the tube wall .H is provided a transparent, conductive tinoxide layer l0, which is connected through a, conductor or a spring [3 to the post-acceleration anode 8., Externally of the tubea. mask I2 is clamped to thebulb in a manner such that the 1 numerals provided in the, mask; are exactly in front of the corresponding luminescent parts of the screen 19. The numeral corresponding to the beam position at a particular instant thus becomes apparently luminescent.

Thegrid 5 is arranged in a manner such that the partial beam currents overlap one anotherin part on the fluorescent screen, so that an .op-

timurn uniformity of luminescence of the surface is obtained, beingfreefrpm troublesome- 4 shadows of the grid wires and being sharply defined, since stray electrons and peripheral electrons, which are excessively deflected by the grids 3 and 5, are retained by thelgallzol of the anode 6. The post-acceleration electrodet' serves to suck off the secondary electrons from the screen 9, so that the latter takes a positive potential and the electrons impinge upon it with greater velocity. Ihe transparent, conductive oxide layer lfl ei's connectedto the post-acceleration electrode B-"bymeans of the-connection I3. If the layer I lobetweenthe-screen 9 and the tube wall II and the fluorescent screen '9 itself are sufliciently con- 'ductive, the post-acceleration anode 8 may, if

desired; :bedispensed with.

An example of, the construction of the grids :3, and .5 and ofj the spacings between the various electrodes now follows: The grid has a pitch of' 1'.-7,2. mms., a wire thickness of 130/[L and is spaced apart in front of the slotted screen at a distance of 1.6 mms. Theflgridi also has a,.pitch of 1.72 ,mms; anda wire thickness-of 130/,u, but it .is spaced apart behind the slotted screen Act a distance of 1.43- mms. The spacing between the slotted screen 4 and the anode 6 is La-mms. and the spacing between the anode 6 and the post-acceleration electrode is 1.5 mms. The apertures of the-anode Shave-a height of .two grid apertures and are arranged in staggered position for the various ,beampositions. The

gauze fl hasapproximately meshes an inch, i. e. a wire thickness of IGO and a pitch of- 260/ The apertures of the post-acceleration electrode 8 are not covered with, gauze. vAta distance of-1A= mms. behind the post-.accelera--- tion electrode 8..is located the fluorescent layer 9, which is separated fromthe tube wall II by a tin-oxide layer l0. Externally of the tube wall- I l isprovidedacel-luloid mask [2.

The electrodes 3 and 5 are connected to the cathode. and the anode=6 is connected to +100 to +250 V3, the post-acceleration electrode 8 to The slotted screen. 4- is connected to 250v.

Fig. 1 shows the travel of the electrons. The

stray electrons and the peripheral electrons M are retained by thegauze 1 and consequently, cannot give rise to phantom images and unsharp edgesof the luminescent. parts.

,It is evident that with other voltages and other dimensions of; the electrodes the gridsmusthave other correspondin dimensions;

What I'claimis:

I; An e-lectric discharge. tube adapted ftO counta succession of pulses comprising an envelope and an electron discharge system within the envelope :andcomprisingaan electron gun capabletof generating a ribboneshaped :beam, .a .pair of deflection electrodes positioned to deflect the beam to obtain agivennumberoflpositions, a first grid electrode haying wires positioned parallel to the direction of deflection of the beam, a first slotted screen electrode-having slots. positioned perpendicu-lar to the. wires o f the first grid electrode, a second grid electrode positioned on the side of the ffirstscreen electrode remote from the electron gun and having wires positioned in register with and parallel to the. wires of the first grid electrode, a second slotted'screen' electrode hav: ing slots positioned in register with..-the slots; :of

the first screen electrode, a gauze covering over a.;

portion of said-second slotted screen electrode, a third slcttedelectrode havingslots positioned in staggered register with the slotsof said secondre n e ec ic and. :W ll 9 Q portion of the inner wall of the envelope in the path of the electron beam.

2. An electric discharge tube as claimed in claim 1 in which the second slotted screen electrode has slots having a cross-sectional dimension at which together with the gauze covering less than 20% of the beam current is passed by the electrode.

3. An electric discharge tube as claimed in claim 1 in which the third slotted electrode is at a positive potential relative to the electron gun and serves as a post-accelerating anode.

4. An electric discharge tube as claimed in claim 1 in which a transparent, conductive tin oxide layer connected to a. source of positive 15 potential is interposed between the fluorescent screen and the inner wall of the envelope.

5. An electric discharge tube as claimed in claim 4 in which the conductive layer is elec- 5 trically connected to the third slotted electrode.

ICLAAS RODENHUIS.

References Cited in the file of this patent UNITED STATES PATENTS 

